CONFRONTO TRA INFORMAZIONI GEOLOGICHE E PEDOLOGICHE SUL CONOIDE DEL CELLINA (FRIULI, ITALIA)

Abstract

Seven soils located on terraces of different ages of an alluvial fan in north-eastern Italy have been compared in terms of their morphology and degree of development. Alluvial deposits deriving from calcareous-dolomitic rocks, with subordinated terrigenous rocks, always represent the parent material. There are no crystalline rocks outcrops in the mountain basin. The geomorphological evolution of the alluvial fan has been strictly controlled both by the still active tectonics of the area and by the long-term variability of climatic factors.
One (Profile F) is located on the Holocene fan and presents a low degree of development, two, profiles C and E, are on the main surface of the Pleistocene fan, dated 10530 ± 100 yBP, conventional 14C age. The different degree of development is probably due to the
difference in parent material, very coarse gravel with boulders in profile C, gravel in profile E. Profile D is on a higher terrace, but is
similar to those on the main surface. Profiles G and B are located on small portions of terraces, probably in a tectonics-affected position, at the very border of the alluvial plain. Profile H is a buried soil, outcropping under a 30m thick gravel deposit.
Extractable iron ratios have also been considered in order to determine whether they are affected by their relative ages. Free ironoxide/Total-iron ratios, according to the AIR and Arduino methods, gave unattended results. It has not been possible to recognise a trend with the increasing age and the range of values obtained is much greater than those known by literature. A possible explanation is in the peculiar characteristics of the area, where even the content of total-iron alone offers a trend of development, as can be evinced by its increasing with relative age and decreasing with depth.